Hybridomas (mouse x mouse) have been prepared to the human breast cancer cell line MCF-7. Clones producing specific antibody have been selected and will be screened vs. live MCF-7 and numerous other normal and tumorogenic human cell lines. Selected clones will be put into BALB/c mice for ascites production. Isotyping, immunofluorescence, cytotoxic and immunoperoxidase will be performed on tumor and normal tissue sections as well as two-dimensional SDS-page analysis to fully characterize the MoAb. Cross-reactivity with other human cells (normal adult & normal fetal, tumor) will be assessed. Diagnostic and immunotherapeutic potential will be determined. This should provide a useful model system for MoAb immunotherapy by transplanting tumors to nude mice. Immunoperoxidase staining of tumor and normal tissue sections will provide further information.